#include "stdio_impl.h"
#include <wchar.h>
#include <errno.h>
#include <limits.h>
#include <string.h>
#include <stdlib.h>
#include "libc.h"

struct cookie {
    wchar_t **bufp;
    size_t *sizep;
    size_t pos;
    wchar_t *buf;
    size_t len;
    size_t space;
    mbstate_t mbs;
};

struct wms_FILE {
    FILE f;
    struct cookie c;
    unsigned char buf[1];
};

static off_t wms_seek(FILE *f, off_t off, int whence)
{
    ssize_t base;
    struct cookie *c = f->cookie;
    if (whence>2U) {
fail:
        errno = EINVAL;
        return -1;
    }
    base = (size_t [3]){0, c->pos, c->len}[whence];
    if (off < -base || off > SSIZE_MAX/4-base) goto fail;
    memset(&c->mbs, 0, sizeof c->mbs);
    return c->pos = base+off;
}

static size_t wms_write(FILE *f, const unsigned char *buf, size_t len)
{
    struct cookie *c = f->cookie;
    size_t len2;
    wchar_t *newbuf;
    if (len + c->pos >= c->space) {
        len2 = 2*c->space+1 | c->pos+len+1;
        if (len2 > SSIZE_MAX/4) return 0;
        newbuf = realloc(c->buf, len2*4);
        if (!newbuf) return 0;
        *c->bufp = c->buf = newbuf;
        memset(c->buf + c->space, 0, 4*(len2 - c->space));
        c->space = len2;
    }
    
    len2 = mbsnrtowcs(c->buf+c->pos, (void *)&buf, len, c->space-c->pos, &c->mbs);
    if (len2 == -1) return 0;
    c->pos += len2;
    if (c->pos >= c->len) c->len = c->pos;
    *c->sizep = c->pos;
    return len;
}

static int wms_close(FILE *f)
{
    return 0;
}

FILE *open_wmemstream(wchar_t **bufp, size_t *sizep)
{
    struct wms_FILE *f;
    wchar_t *buf;

    if (!(f=malloc(sizeof *f))) return 0;
    if (!(buf=malloc(sizeof *buf))) {
        free(f);
        return 0;
    }
    memset(&f->f, 0, sizeof f->f);
    memset(&f->c, 0, sizeof f->c);
    f->f.cookie = &f->c;

    f->c.bufp = bufp;
    f->c.sizep = sizep;
    f->c.pos = f->c.len = f->c.space = *sizep = 0;
    f->c.buf = *bufp = buf;
    *buf = 0;

    f->f.flags = F_NORD;
    f->f.fd = -1;
    f->f.buf = f->buf;
    f->f.buf_size = 0;
    f->f.lbf = EOF;
    f->f.write = wms_write;
    f->f.seek = wms_seek;
    f->f.close = wms_close;

#ifdef OS_OPTION_NUTTX_VFS
    pthread_mutexattr_t attr;

    f->f.owner = -1;
    if (pthread_mutexattr_init(&attr) != 0 
            || pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE) != 0
            || pthread_mutex_init(&f->f.mutex, &attr) != 0) {
        free(f);
        return 0;
    }
#else
    if (!libc.threaded) f->f.lock = -1;
#endif /* OS_OPTION_NUTTX_VFS */

    fwide(&f->f, 1);

    return __ofl_add(&f->f);
}
